It is known that the grip conditions of a tyre running on a given ground, and especially its maximum grip coefficient, vary very greatly depending on the running conditions. Among the main factors are the type of road on which the wheel is running, the weather conditions and the temperature.
It is particularly advantageous to know in real time the grip conditions and especially the maximum grip coefficient of the running wheel in order to determine whether or not it is close to losing its grip on the ground.
This information relating to the grip of the wheel may be transmitted to the driver of the vehicle with which the wheel is fitted, so that he can adapt his driving accordingly, or to an electronic device for monitoring the road holding of the vehicle.
It has been shown in the prior art, especially in WO 03/066400, that it is possible to determine the maximum grip coefficient of the tyre of a wheel from measurements of the three components of the forces applied on the tyre, namely the self-alignment torque, the tyre inflation pressure and the tyre camber.
In particular, the above document specifies that it is possible to determine the maximum grip coefficient when there is a region of slip in the contact area between the running tyre and the ground. As soon as this region of slip occurs, for example for the same transverse force, the self-alignment torque is a monotonic function of the maximum grip coefficient.
This method of determining the maximum grip coefficient is limited as it can be implemented only under large acceleration or braking forces or on a bend.
Document FR 2 916 412 presents a motor-vehicle wheel assembly by means of a wheel holder associated with the vehicle by at least one pivot so that the plane of the wheel can make a substantially zero first toe angle and a non-zero second toe angle. The assembly comprises a binary actuator with a control device designed to shift the plane of the wheel under given running conditions.